Lorentz invariance of the \(S\) -matrix has no obvious connection to the decoupling. Without decoupling there will be a mismatch between the number of Ward-identities of the asymptotic symmetries and the number of soft \(S\) -matrix elements. So, in order to derive soft-theorems from the corresponding Ward-identities, decoupling is crucial. It seems that the correct explanation of the universal rules we have stated, goes beyond the "asymptotic symmetry - soft theorem" correspondence. In fact there are some indications, that an Euclidean CFT living on the celestial sphere holographically computes the \(S\) -matrix elements in the asymptotically flat space [1]}, [2]}, [3]}, [4]}, [5]}, [6]}, [7]}, [8]}, [9]}, [10]}, [11]}, [12]}, [13]}, [14]}, [15]}, [16]}, [17]}, [18]}, [19]}, [20]}. If this is true then the dual CFT may provide a microscopic explanation of the universality. Another avenue will be to understand the asymptotic symmetries in flat space-time from the string theory point of view along the line of [21]}, [22]}, [23]}, [19]}, [17]}. We leave these questions for future study.
